Villager despawing

I had about 20 villagers next to an iron golem farm in a 2x21 space. 13 of these villagers were name tagged Librarians with locked in trades. There was no was for mobs to jump in this space or spawn into this place. I came back from a different area and they were all despawned….The only possible thing I can think of could be that lightening struck them 3-4 times which converted all of them to witches that then despawned…. This may be very unlikely as I also had another villager 2-3 blocks away from this space in a 1x1 space that was suspended in air 3 blocks up who also despawned. There are no beds within a 5 block radius of any villager just lecturns.